Gates Standard Ports (sometimes called a dome port) are optically corrected to provide a normalized view of the underwater world. That is, they compensate for distortions or magnifications inherent to the underwater realm: the camera view below water is almost exactly that above water. A standard port is made of optical-grade acrylic or polycarbonate and allows little or no zoom-through capability (the result of being a negative lens underwater, and forcing the camera to focus on a virtual image).